Some think the seeds need to be planted in late summer or early fall. I've been planting them in December for sometime now with fairly good results. No matter if the seeds are purchased or collected, it's helpful to soak them before planting. Full sun and well drained soil helps. The vines will need something for the tendrils to climb. However, they would probably grow like weeds almost anywhere.
Continual harvesting of the blossoms will help develop more flowers. Once the weather gets hot, sweet pea season is over. Let the blossoms go to seed and collect them for the next year.
Who doesn't enjoy a nice bouquet of sweet peas?